Introduction
Cross drain techniques such as open-top cross drains and surface water diverters
using conventional materials have been in use for years. New cross drain techniques
are emerging due to the availability of new materials and field innovations.
Some of these techniques are being developed and have not been applied in the
field. The objective of this report is to disseminate information on new materials
and techniques. In addition, new, innovative application of existing materials
or techniques are reported. Some of the materials presented in this report are
subject to local availability.

Report Overview
A synopsis of the information contained in the report is provided in table 1,
with further discussion in the following pages. When available, cost information
is provided as a reference only, as prices and rates vary from location to location.
Definitions of terms used in this document are included in appendix A; a cost
summary for open-top pipe culverts is included in appendix B.

Background
Two methods were used to gather information for this report: A market search,
including publications in print and on the Internet; and a survey to U.S. Department
of Agriculture (USDA) Forest Service personnel. Since the method or technique
for using cross drains is specific to local geography and conditions, pertinent
local information is included. Both search methods identified available techniques,
some of which are not new, but are included to disseminate information and perhaps
to stimulate new applications.

Open-Top Pipe
Culvert
Information for this section was taken from Using Open-Top Pipe Culverts to
Control Surface Water on Steep Road Grades by James N. Kochenderfer, Northeastern
Forest Experiment Station, General Technical Report NE-194, with the author’s
permission. These open-top pipe culverts have been installed and used successfully
on “minimum standard” forest truck roads in proximity to the Fernow
Experimental Forest near Parsons, WV.

Open-top pipe culverts are effective
in controlling surface water on portions of minimum-standard roads where road
grades exceed 10 percent. The open-top pipe culvert is not recommended as the
primary means of water control but as a supplemental device that can be used
on steep road sections where broad base dips are not recommended. Open-top pipe
culverts offer land managers an alternative to crowning and ditching roadbeds
for water control. Unlike culverts constructed from wood, the open-top pipe
culvert is a relatively permanent water control device; however, these culverts
may be salvaged and used on other roads as the need arises. The cost of an open-top
pipe culvert is comparable to that of a gravel broad-based dip.

Construction
Using a chalk line, mark two parallel lines 3 in (75 mm) apart along the length
of the steel pipe. The lines create longitudinal borders for the inlet slots.
Mark slot locations within the two parallel lines. A welding marker works well
for marking the slots. Slots 24-in long by 3-in wide (600-mm by 75-mm) work
well with an 8-in (200-mm) diameter pipe (figure 1). Larger slots may be used
in larger diameter pipes. Experience has shown that slots this size do not damage
tires and are wide enough to allow the pipe to be cleaned. Spacing slots at
least 6 in (150 mm) apart will prevent the pipe from collapsing under a heavy
wheel load. To provide structural rigidity, leave at least 18 in (450 mm) of
solid pipe at both ends.

Installation
The open-top pipe culverts have been installed with a downslope skew ranging
from 45 to 65° with an average of 54° skew and average road grade of
12 percent. It is important to minimize skew to improve its self-cleaning capability.
Skew in this document is measured from the road centerline (figure 2).

Culvert installation may be done manually or with the use of a small dozer.
The culvert is installed with the top of the pipe 3 in (75 mm) below the surface.
The roadbed is then beveled back about 18 in (450 mm) on each side of the culvert.
The skew and depth is better controlled when installed manually. However, a
10-in (250-mm) diameter pipe weighs about 31 lb/ft (46 kg/m) and an 8-in (200-mm)
diameter pipe weighs about 25 lb/ft (37 kg/m); therefore, a typical culvert
section would weigh between 500 and 600 lb (227 kg and 272 kg). Two people can
move and position the culvert by sliding or rolling it. Lifting the culvert
requires a small dozer. Once installed, the outfall may be armored with rocks
and a half-round plastic pipe.

Discussion
Open-top pipe culverts are being used in central Appalachia. The average culvert
length is 20 ft (6 m). The 20-ft (6-m) length allows for enough skew on a 15-ft-
(4.6-m-) wide road. Both 8-in- (200-mm-) and 10-in- (250-mm-) diameter pipe
were used. The 8-in (200-mm) pipe was preferred because it is generally less
expensive, requires a shallower trench, and is easier to maneuver by hand than
the larger pipe.

While open-top pipe culverts function
well on steeper grades, it is desirable to keep road grades low, both to facilitate
water control and to provide maximum use. These culverts also can be used where
rocky subgrades might prohibit construction of broad-based dips and on road
sections between landings and highways to prevent water from running on to highways.

A tool for cleaning open-top pipe
culverts is shown in figure 3.

It is important to space open-top
pipe culverts properly so that water can be handled in small amounts. For design,
use local cross drain spacing formulas for open-top-drains.

Figure
1—Using
a cutting torch to cut slots in a heavy walled pipe.

Figure
2—Layout and dimensions of an open-top pipe culvert.

Figure
3—A tool
for cleaning open-top pipe culverts is made by bending a 5-ft (1.5 m)
piece of 0.75-in (19-mm) pipe two ways and welding it to a 4- by 5-in
(100- by 127-mm) shaped peice of metal cut from a pipe.

Portable Road
Spillway
The portable road spillway (figures 4a and 4b), a prefabricated, portable, reusable
cross drain works on the principle of diverting silt and debris encountered
in typical surface runoff into a series of pre-established settling ponds. An
illustration of a typical application is shown in figure 5. The settling ponds
are constructed on the low side of the road spillway and are made out of native
material found at the site. The settling ponds slow the movement of water both
from the natural drainage system and from roadway runoff. Sediment and debris
are settled out within the ponds before water is discharged to the local water
course. Heavy equipment traffic typically associated with logging and mining
roads is easily handled by the Portable Road Spillway.

Material

Structural steel tubing, either
20 ft (6 m) or 24 ft (7.2 m)

#5 Grade-40 rebar

Type-10 Portland Cement redi-mix
precast

Construction
The portable road spillway, distributed by RayMac Environmental Services, consists
of a structural steel tubing grid sitting on top of precast L-shaped abutments.
It is constructed in three separate sections: two concrete abutments, and one
steel top grid. The concrete abutments are made of 3,000 psi (20 MPa) redi-mix
concrete reinforced by #5, grade-40 rebar. When fully assembled, each abutment
weighs 10,000 lb (4,536 kg). The 2,500-lb (1,134-kg) top grid is constructed
of structural grade steel (figure 6).

Installation
The entire portable road spillway can be transported to the site in a standard
dump truck. An excavator is used to dig a trench across the road to accommodate
the spillway and place the abutments. Once the proper separation of abutments
has been established, the excavator places the steel grid on top of the abutments
and backfills the trench (figure 7).

Maintenance
The steel grid may be removed to clear the trench of obstructions and sludge.
Depending on the amount of debris or sediment present, a small excavator may
be necessary for cleaning out the trench.

Figure
4a and 4b—Two
views of the Portable Road Spillway.

Figure
5—Typical application of the Portable Road Spillway.

Figure
6—Portable Road Spillway assembly.

Figure
7—Sectional view of the Portable Road Spillway.

Metal Water
Bar
The metal water bar is an innovative example of using a standard “W”-beam
guardrail. It combines two common cross drain techniques, the water bar and
an open-top drain.

Material

Standard “W” beam
guardrail, nominal thickness of 0.135 in (3.4 mm)

Mild steel flat bar 0.25-in (6.4-mm)
thick by 4-in (100-mm) wide.

Construction
Construct anchors as shown in figure 8 using the 0.25-in (6.4-mm) steel bars.
Weld the completed anchors to the “W”-beam guardrail at even intervals
as shown in figure 8. Guardrail length comes in standard 12.5-ft (3.8-m) or
25-ft (7.5-m) length. Cut off the excess to achieve an appropriate length, including
the additional length needed for the skew angle. The smaller the skew angle,
the longer the length has to be over the length of the road. The length will
be determined by the following formula:

Length = road width / sine (skew angle) + installation tolerance

When using 12.5-ft (3.8-m) lengths,
the two pieces should be butt-welded or overlapped with the downgrade section
beneath the upgrade section. All holes on the guardrail must be permanently
plugged. All nongalvanized, nontreated areas must be painted with primer.

Installation
Install the metal water bar with a maximum 60° downslope skew. The installation
can either be done manually or with the help of a dozer for the heavy lifting.
Measure the maximum height of the metal bar assembly, once constructed. This
will determine the depth of the trench to be dug. The depth of the trench should
be about 3-in (75-mm) deeper than the maximum height of the assembly. A trench
wider than the width of the water bar assembly is necessary not only to more
accurately position the water bar, but also to allow for a margin of error.
The water bar is installed with the top of the “W” beam about 3-in
(75-mm) below the road surface. Once installed, the road could be beveled back
about 18 in (450 mm).

A rock outfall may be constructed
at the end of the water bar using 3- to 12-in- (75- to 300-mm-) diameter rock.
The outfall should be approximately 2-ft (0.6-m) wide and at least 6-in (150-mm)
deep.

Figure
8—Metal water bar construction details.

Rubber Water
Diverters
Rubber skirting or used conveyor belts are utilized to make water diverters.
The water diverters direct water off the surface of the road. Like the other
cross drains, the skew angle is critical to the function of the water diverter.
Rubber diverters require minimal maintenance; however, to reduce possible damage
by grading operations, use an object marker to identify location of diverters.

Material

Rubber skirting: 5-ply, 1/2-in
thick by 12-in wide by 20-ft long (13-mm by 300-mm by 6-m).

Timber: 4- by 8-in by 20-ft (100-
by 200-mm by 6-m) rough sawn No. 2 or better, pressure treated for a design
life of 20 years.

Construction
Secure the rubber skirting on the 4-in (100-mm) face of the pressure treated
timber, using the lag screws and washers. Figure 9 illustrates the construction
of the diverter.

An alternate method of construction
uses conveyor belting.

Material

Conveyor belt: 0.438- by 12-in
wide by 20-ft long (11-mm by 300-mm by 6-m).

Timber: 2-in by 6-in by 20-ft
(50-mm by 150-mm by 6-m) rough sawn No. 2 or better, pressure treated for
a design life of 20 years.

Construction
The bottom of the conveyor belt is “sandwiched” between the boards.

Installation
Install the rubber diverter with a maximum 60° downslope skew. A trench
is dug approximately 36-in (900-mm) wide. The diverter is installed so that
approximately 3 to 4 in (75 to 100 mm) is above the road surface. The density
of the backfill must equal or exceed the density of the surrounding material.
The backfill material must be either the same material as the road or be crushed
aggregate. Figure 10 provides installation details.

Figure
9—Rubber water diverter detail.

Figure
10—Installation detail of rubber water diverter.

Precast Concrete Trough
This cross drain device could be classified under open-top drains. Similar to
the devices in the open-top category, this concrete trough allows surface water
to accumulate through the open top (figure 11).

Material

Concrete: 10 ft3 (0.3 m3) for
a 7-in by 14-in by 14-ft (176-mm by 350-mm by 4.3-m) trough.

#4 Grade-40 rebar

Installation
The soil around both sides of the cross drain must be compacted. The concrete
trough must be installed with a maximum 60° skew and at least a 4 percent
fall.

Polyethylene Pipe
Polyethylene pipe has approximately twice the service life of corrugated metal
pipe and is lighter and easier to install. The anticipated service life of high
density polyethylene (HDPE) is approximately 75 years. Corrugated steel has
an anticipated service life of 40 years. HDPE is strong enough to endure soil
pressures at a depth of up to 100 ft, and is durable enough to handle runoff
containing abrasive bedload.

Two polyethylene products were evaluated
for this project: Advance Drainage Systems (ADS) N-12 and ADS N-12 HC. ADS N-12
is a HDPE drainage pipe available in diameters ranging from 4 to 36 in (100
to 900 mm). The pipe is a combination of an angular corrugated exterior for
strength and a smooth inner wall for maximum flow capacity. ADS N-12 HC comes
in 10-in (250-mm), 12-in (300-mm), 15-in (380-mm), 18-in (450-mm), 24-in (600-mm),
30-in (760-mm), 36-in (900-mm), 42-in (1-m) and 48-in (1.2-m) diameters. The
N-12 HC has smooth inner and outer walls and a “honeycomb” wall
section for structural strength and ring stiffness. The HDPE pipe withstands
vertical pressure by transferring the load to the surrounding soil. N-12 and
N-12 HC will support HS-20 live loads under 12 in (300 mm) of cover. This is
equivalent to values specified for corrugated metal and concrete pipe. HS-20
loading designation is specified by American Association of State Highway and
Transportation Officials. The HS-20 live loading is comparable to a 3-axle truck
with an 8,000-lb (3,630-kg) load on the front axle and a 32,000-lb (14,500-kg)
load on the two rear axles. Maximum cover will vary with conditions, but can
usually extend from 30 to 50 ft (9 to 15 m). Table 2 provides a weight comparison
of HDPE, clay or concrete, and corrugated metal pipe. Figure 12 graphically
represents corrosion resistance (recommended pH range).

Table
2—Weight comparison of three pipe types by inside diameter

Inside Diameter in inches (mm)

ADS N-12/N-12 HC HDPE Pipe in
lb/ft (kg/m)

Clay or Concrete in lb/ft (kg/m)

Corrugated Metal in lb/ft (kg/m)

15 ( 380)

4.6 ( 7)

103 ( 153)

12.9 (19)

18 ( 450)

8.4 (12.5)

131 ( 195)

15.8 (23.5)

24 ( 600)

11.5 (17)

217 ( 323)

19.4 (29)

30 ( 760)

15.4 (23)

384 ( 571.5)

30.0 (45)

36 ( 900)

18.1 (27)

524 ( 780)

36.0 (54)

42 (1,000)

26.5 (38)

650 ( 967)

57.0 (85)

48 (1,200)

32.0 (48)

780 (1,161)

65.0 (97)

Used Gas Pipe
Used gas pipe has been utilized in the Allegheny National Forest of Region 9,
where the pipe is available locally. The wall thickness on the steel pipe is
four times greater than that of conventional corrugated metal pipe (CMP). Thicker
walls allow the pipe to be installed in areas where the minimum coverage of
12 in (300 mm) for CMP or HDPE pipe is difficult to achieve. Although the procurement
and installation costs are higher than for new CMP, the anticipated service
life is longer.

Driveable and Durable “Hump”
This cross drain technique remains in the concept stage as illustrated in figure
13 and is included in this report to generate interest and possible implementation.
Like the rubber water diverter, the hump diverts surface flow off the road while
requiring minimal modification to the road profile. Several stages would allow
for sedimentation while still preserving diversion capability and extending
periods between required maintenance. Hump length and height should be tailored
to road grade, climate, expected flows, soil type, and design vehicle. Possible
materials to test include rubber, rubber strapping, plastic, concrete, metal,
and wood.

Conclusion
The application of cross drain techniques will have varying results due to local
geographical conditions. The techniques are presented to provide information
on products that have been successful in other areas and also to stimulate innovative
applications.

Figure
12—Corrosion
resistance 9recommended pH range).

Figure
13—A dreveable and durable "hump".

Appendixes

Appendix ADefinitionsArmoring—protective covering, such as rock, vegetation,
or engineered materials used to protect stream banks, fill- or cut-slopes, or
drainage structure outflows from erosion.

Cross Drain—a
ditch relief culvert or other structure or shaping of the traveled way designed
to capture and remove surface water from the traveled way or other road surfaces.

Crown—traveled-way
surface shaping with the high point in the middle, causing surface runoff to
flow both toward the uphill shoulder or ditch and toward the downhill shoulder.

Culvert—a
conduit or passageway under a road or other obstruction designed for the passage
of water, debris, sediment, and fish, backfilled with embankment material.

Inslope—traveled
way surface shape with high point on downhill shoulder, causing runoff to flow
toward the toe of the backslope or inboard ditch.

Outslope—traveled-way
surface shaping with the high point on the uphill shoulder, causing surface
runoff to flow toward and over the downhill shoulder.

Pipe—a
culvert that is circular in cross section.
Road—a general term denoting a mode for travel by vehicles greater than
50 in (1.3 m) in width.

Roadbed—the
graded portion of a road between the intersection of subgrade and side slopes,
excluding that portion of the ditch below the subgrade.

Sediment—deposition
of materials eroded and transported from locations higher in the watershed.

Service Life—the
length of time for which a facility is expected to provide a specified service.

Skew—the
angle of deviation from a reference line. In this document, the reference line
is the road centerline.

Subgrade—the
layers of roadbed that come up to the top surface, upon which subbase, base,
or surface course is constructed. For roads without base course or surface course,
that portion of roadbed prepared as the finished wearing surface.

Surface Drainage—the
concentration and flow of surface water on roads and related surfaces and in
ditches.

Information contained
in this document has been developed for the guidance of employees of the
U.S. Department of Agriculture (USDA) Forest Service, its contractors,
and cooperating Federal and State agencies. The USDA Forest Service assumes
no responsibility for the interpretation or use of this information by
other than its own employees. The use of trade, firm, or corporation names
is for the information and convenience of the reader. Such use does not
constitute an official evaluation, conclusion, recommendation, endorsement,
or approval of any product or service to the exclusion of others that
may be suitable.

The U.S. Department
of Agriculture (USDA) prohibits discrimination in all its programs and
activities on the basis of race, color, national origin, sex, religion,
age, disability, political beliefs, sexual orientation, or marital or
family status. (Not all prohibited bases apply to all programs.) Persons
with disabilities who require alternative means for communication of program
information (Braille, large print, audiotape, etc.) should contact USDA’s
TARGET Center at (202) 720-2600 (voice and TDD).